In a long term evolution advanced (LTF-A) system, to increase the throughput of a cell and reduce the interference between users, each cell may be configured with 16, 32, 64 or more transmitting antennae for beam forming. A base station configures a channel state information reference signal (CSI RS) for each user equipment (UE), and the UE measures channel state information (CSI) of a channel using the channel state information reference signal (CSI RS) and then feeds back the channel state information to the base station. As a CSI RS, previous to 3GPP Version 12, is designed according to the actual number of physical antennae, and there are eight ports at most in the CSI RS previous to 3GPP Version 12, and there are eight resource units at most in each physical resource block, as shown in FIG. 1. At present, the number of physical antennae increases greatly. If the number of ports is designed still according to the number of the physical antennae, the resources occupied by CSI RSs in each resource block will increase greatly. How to reduce resources occupied by CSI RSs becomes a problem to be researched.
In the LTF-A system, the resources of CSI RSs are provided for UE to measure channel state information. The channel state information includes a rank indicator (RI), a channel quality indicator (CQI) and a pre-coding matrix indicator (PMI), etc. At present, the CSI RS is sent from a base station to UE, and a corresponding CSI RS original signal is directly transmitted in the bandwidth of the whole downlink system, as shown in FIG. 2. The UE acquires the RI, CQI and PMI by measuring the CSI RSs. Specifically, the method for measuring the CQI is as follows: channel information is measured and estimated through CSI RSs, and then it is assumed that a specific PMI and RI is used at a signal transmitting terminal to measure the corresponding CQI, that is, the measurement of the CQI is performed based on a specific PMI.
In the LTF-A system, as shown in FIG. 3, antennae are distributed horizontally, and the ports of the antennae are also arranged horizontally. By using a one-dimensional antenna array, beam forming is directed to different direction angles of the horizontal plane. However, in fact, terminals may have different direction angles in the vertical plane due to different locations in the vertical direction and different distances away from a base station. As shown in FIG. 4, by using a two-dimensional antenna array, by beam forming in the vertical plane and beam forming in the horizontal plane, both the interference between terminals at different vertical direction angles and the interference between terminals at different horizontal direction angles are further reduced, thereby further increasing the throughout of a cell, as shown in FIG. 5.